1. Field of the Invention
The present invention pertains to a component such as a diode, a triode or a flat and integrated cathodoluminescent display device, and to a method for the fabrication of a device such as this.
2. Description of the Prior Art
The recent literature includes a number of publications relating to cathodoluminescent display devices. Apart from the standard electron gun with its system of excitation of a luminophor in a "television tube" type of vacuum tube, there are new approaches now emerging. Thus, one current trend that can be seen consists in the use of matrix arrangements of microguns, the working of which is multiplexed by means of an adapted electronic circuitry. An embodiment such as this is given in an article by R. Meyer and coll., "Microtips Fluorescent Display", presented at the "Japan Display 1986" conference. The microguns are formed by molybdenum tips, and the electrons are extracted by field effect between the tip and a grid located at the top of the tip. An anode, made of a luminophor material, is positioned at a distance of about 100 .mu.m from the plane of the gate.
It is possible to envisage a structure that is similar but has its microtips made by using no longer a matrix of field effect microtips but a matrix of cold microcathodes made on semiconductor material (Si for example). This type of cathode uses a semiconducting surface treated so as to have a negative electron affinity. As for Si, the surface treatment used to obtain this property consists in the successive adsorption on a surface (100), reconstructed by heat treatment, of a caesium monolayer and an oxygen monolayer. More details on this caesiation technique will be found in the articles by B. Goldstein (Surf. Sci. 47, 1975, p. 143) and J.D. Levine (Surf. Sci 34, 1973, p. 90).
Under the above-described conditions of caesiation of p type Si, and because of:
(a) the considerable reduction i the level of the vacuum;
(b) the curvature of the conduction bands on the surface,
the electrons located at the minimum level of the conduction band, in the volume of the material, have an energy level which is greater than that of the level of the vacuum the so-called situation of "negative" electron affinity is obtained.
If the layer of p type silicon thus treated is placed on an n type substrate, and if the junction thus obtained is forward biased, there is an injection of electrons that are emitted in the vacuum after going through the p type layer.
The making of a cold cathode such as this has been described by E.S. Kohn (IEEE Transactions on Electron Devices, ED-20, No. 3, 1973, p. 321).
E. S. Kohn has used this type of cathode to reproduce, on a screen supporting a luminiphor and placed at 0.5 mm from the plane of the cathode, characters etched in silicon and treated, according to the above description, to have negative electron affinity.
The drawback of all these devices (devices with emission by field effect, or devices using silicon cold cathodes) is that they can work only under ultrahigh vacuum conditions. This is particularly true for caesiated silicon surfaces, where the least adsorption of foreign atoms is liable to raise the energy state of the level of the vacuum, thus seriously affecting the emissive properties of the surface.